Bosses are commonly formed on the surfaces of plastic moldings. A boss may include a shaft opening to receive a threaded fasten used to mount a second molded piece or other mechanical item. The boss commonly has a substantial volume relative to the adjacent wall thickness. As a result during molding process boss volume contracts, and sucks in the surrounding material. This can result in a cavitation spot on the wall opposite the boss. The cavitation spot is an irregular depression, and in the case of a high quality surface product like an aluminized optical reflector, the cavitation spot is a defect. There is a need to eliminate such defects in high quality surfaces while still providing for boss mountings.